Study On The On-line Monitoring System Of Power Quality Of Grid-connected Photovoltaic Power Station

As the energy crisis and environmental pollution become more and more serious,solar energy as an important part of renewable energy is widely concerned.And its main utilization form is photovoltaic power generation.With the increasing penetration of photovoltaic power generation in the power grid,large photovoltaic power stations may cause serious power quality problems due to the uncertainty of optical resources or the operation quality of the converter,affecting the normal operation of the public power grid.So,a quick and accurate online monitoring of the power quality of the solar system is very important for the safety and stability of the power grid and the power plant.According to the characteristics of the photovoltaic power station,an on-line monitoring system for grid-connected photovoltaic power stations based on the CompactRIO platform is designed in paper.And the analysis and calculation of various power quality parameters are completed to ensure safe and effective operation of the photovoltaic power station and power grid.At first,the development status and trend of power quality monitoring technology and devices at home and abroad are reviewed.Then the structure of grid-connected photovoltaic power station and its various parts may be the impact of power quality,and analyzes the definition,calculation method and potential harm of electric energy quality parameter to be monitored are introduced.Later,the national standard of power quality which are the design basis of this system are listed.After then,in view of the large photovoltaic power station into the public grid could cause the power quality problem,a set of power quality online monitoring system design is proposed.The hardware of signal conditioning circuits are designed and the selection of signal acquisition module of power quality are completed.And the fast acquisition and processing algorithm programming of power quality signal is realized by using LabVIEW graphical programming tool.The fast acquisition and processing algorithm of power quality signal is designed by using LabVIEW graphical programming tool.In order to further satisfy the high accuracy demand of the grid-connected photovoltaic power station for harmonic detection,a four-spectral-line interpolation FFT harmonic detection algorithm for the hybrid convolution window is proposed,aiming at the reasonsof the accuracy of the traditional window interpolation algorithm.By using the more excellent spectral characteristics of the hybrid convolution window and effectively influence the effect of fence effect of the four-spectral-line interpolation algorithm,the calibration formula for the four-spectral-line interpolation of the hybrid convoluted window is calculated.And the harmonic parameters are obtained more accurately.Finally,the performance of each module of this system are tested by simulation and experiment.The results show that the system has high accuracy and adaptability,which can meet the demand of online monitoring of power quality of grid-connected photovoltaic power station.The significance of this project is that,through the study on the on-line monitoring of power quality of the grid-connected photovoltaic power station,the operation state of the power station is controlled in real time to provide guarantee for its safe and stable operation.